Non-sticking armature structure for electromagnet



H' 8 In r4 mvENToR ATTORNEY W. M. O'NEIL Filed May 25, 1964 July 5, 1966 NoN-SMOKING ARMATURE STRUCTURE FOR ELECTROMAGNET n ai so 42 4 64 56 6| e5 34 49 6.,

eo e4 36 65 6l 42 I es WILLIAM MARSHALLONEIL FIG. 2

FIG. 3

United States Patent O 3 259 812 NUN-STICKING ARMTURE STRUCTURE FOR ELECTRQMAGNET William Marshall ONeil, Oak Park, Ill., assignor lto Teletype Corporation, Skokie, Ill., a corporation of Dela- Wre Filed May 25, 1964, Ser. No. 369,996 6 Claims. (Cl. 317-194) This invention relates to an electromagnet structure and more particularly to a selector magnet for a printing telegraph receiver provided with a non-sticking armature.

Selector magnets are used in printing telegraph apparatus to translate incoming message carrying electrical impulses into mechanical movements, Which are in turn used to control the printing of the message, in the manner, for example, described in United States Patent No. 2,595,745, granted to W. I. Zenner on May 6, 1952. It is very important that these selector magnets be able to respond quickly and positively to the incoming electrical impulses because these impulses are of short duration and 'are received in very rapid succession. To this end it is important that the armature of the selector magnet move away from the pole faces of the magnet quickly and positively when one electrical impulse is completed so that it is ready to respond to the next electrical impulse. Selector magnet armatures have in the past had a tendency, called stickiness, not -to move away from the pole faces of the magnet quickly, this tendency beh ing the result of an unintentional accumulation of oil between the pole faces of the magnet and the armature and also being the result of the slow decay of flux in the core of the magnet.

Accordingly, an object of this invention is to provide an electromagnet the armature of which quickly and positively responds to electrical signals.

Another object of this invention is to provide an armature structure for a selector magnet which does not stick to the pole faces of the magnet.

Still another object of this invention is to provide an armature arrangement for a selector magnet which, upon deenerg-iz-ation of the magnet, quickly and positively moves away from the pole faces of the magnet.

According to the preferred emibodiment of the invention these objects are obtained -by providing a structure wherein the armature, in being attracted to the magnet core, rocks about two pivots, one of which is on the frame of the magnet and the other of which is on the armartrue. |Ilhe armature is attached to the frame -by means of a flexible connecting member and is biased away from the core of the magnet by a spring. rDhe two pivots, the connecting member and the spring are located in such positions that when the arma-ture rocks about the lirst pivot the lever arm through which the spring operates on the armature is of relatively short length whereas When the armature rocks about the second pivot the lever arm is considerably lengthened and therefore the elfective force of the spring in biasing lthe armature away from the core is greatly increased. This is achieved by making the flexible connecting member distort into a curved configuration when the armature rocks about the second pivot, thereby allowing the armature to disassociate itself from fthe lirst pivot. Since the effect of the spring on the armature is increased when the armature rocks about the second pivot, the spring force which is applied to the armature is very large when the armature is in its attracted position. This causes the armature to resist sticking to the core upon release and causes the armature to quickly and positively move away from the core.

A more complete understanding of the invention may ice be had from the following detailed description when considered in conjunction with `the -accompanying drawings wherein:

FIG. 1 is a front view of the selector magnet of the present invention showing the armature in its retracted position and having part of one of the pole shoes and part of the armature extension broken away to show a pole shoe insert and a downstop for the armature;

FIG. 2 is a fragmentary fron-t View of the selector magnet showing the armature in la partially attracted position and having part of the armature and part of the armature support bl-ock broken away to show an armature insert and a retracting spring for the armature, and

FIG. 3 is a fragmentary front View of the selector magnet showing the armature in its fully attracted position.

In the drawings, particular reference being had to FIG. l, there is illustrated a selector magnet assembly 11 for translating incoming message representing electrical impulses into mechanical movements, which movements may be used to control the :printing of the message in the manner described in United States Patent No. 2,595,- 745, granted to W. I. Zenner on May 6, 1952.

The magnet assembly 11 includes a frame member 12 upon which are attached the variaus parts and subassemblies of the magnet. Frame member 12 has 4formed therein two lholes 13 through which appropriate fasteners may be passed so that the magnet may be attached to any suitable support. The frame member 12 also thas raised portions 14, 15 and 16, the front surfaces of which form a plane which is parallel to and spaced from the front of the frame. Upon the plane surfaces thus provided there is mounted ya Ushaped core 117 which is attached to the raised portions 14, 15, and 16 lby bolts 22. When the core 17 is attached in this manner it is held in a spaced relationship to rthe frame 12 thereby 1allowing a pair of coils 18 to be slidably mounted on the legs 4of the core without being in contact with the frame. The coils 18 are urged against upper surfaces 19 and 20 of the raised portions 15 and 16 by the camel-back shaped spring 21 which bears against raised portion 14.

A pair of pole shoes 25 and 26 are individually attached to the raised portions 15 and 16 respectively at the time the fra-me member 12 is cast by causing the material which forms the frame member 12 to partially surround the pole shoes 25 and 26. When the core 17 is attached to the frame member 12, the pole shoes 25 and 26 will thus |be positioned directly below :and in contact with the downwardly extending portions 27 and 28 of the legs off the core 17. Thus, when current is supplied to the coils 18 a flux path is generated through the core 17 and the pole shoes 25 land 26. The core 17 may be constructed from permalloy laminations in the usual manner and the pole shoes 25 and 26 are preferably formed from sintered iron.

Attached t-o the right-hand end of the frame 12 are a pair of spaced hinge blocks 30 and 31 which are interconnected by a web 32. Attached to the hinge blocks 30 and 31 are downstop 34, spring support member 37 and flexible connecting member 40 (FIGS. 1 and 2). Downstop member 34 is bifurcated to provide a pair of mountin-g arms 35 and a leftwardly extending blocking arm 36. The arms 35 are spaced apart an amount equal to the spacing of the hinge blocks 30 and 31 and the lef-twardly extending arm 36 serves as a downstop for the armature 45. The spring support member 37 is also bifurcated to provide a pair of arms 38 and an upwardly and rightwardly extending arm 39. The arms 38 are also spaced apart an amount equal -to the spacing of the hinge blocks 30 and 31 and the upwardly and rightwardly extending arm 39 serves to support an end of a retracting spring 52 which is attached by means of an eye bolt 53 and a lock nut 54. Flexible connecting member 40 is bifurcated to provide mounting arms 41 and a leftwardly extending armature support arm 42. The arms 41 are also spaced apart an amount equal to the spacing of the hinge blocks 30 and 31 and the leftwardly extending arm 42 serves to support the armature 45 in a manner which will be hereinafter described. Arms 35, 38 and 41 are attached to the hinge blocks 30 and 41 by means of a pair of threaded fasteners 43 and 44 and, as has been described hereinbefore, each of the arms are spaced apar-t an amoun-t equal to the spacing of the hinge blocks 30 and 31. This spacing provides a channel in the area of the web 32 through which the retracting spring 52 may pass so that it may be attached to a projecting arm 67 of the armature 45.

The armature 45 is attached to the leftwardly extending arm 42 of the flexible connecting member 40 by means of a pair of rivets 46. A downstop button 47 is attached to the armature in a position to cooperate with the downstop arm 34 and limit the :travel of the armature away from pole faces 64 and 65 on the pole shoes 25 and 26. Armature extension 48 is attached to the armature 45 by means of the downstop button 47 and a rivet 49 located between the rivets 46. The armature extension 48 moves with the armature as it travels to and from the pole shoes 25 and the movements of the armature extension are employed by the various mechanisms of the above-identified patent to translate the incoming message signals into mechanical movements, which in turn control the printing of the message.

Also attached to the armature 45 are a pair of antifreeze bu-ttons 60 and 61. These antifreeze buttons cooperate with a second pair of antifreeze buttons 62 and 63, which are mounted in the pole shoes 25 and 26, respectively, flush with the pole faces 64 and 65, to limit the travel of the armature as it moves toward the pole faces 64 and 65 upon energization of the coils 18. The antifreeze buttons 60, 61, 62 and 63 serve to prevent the armature 45 from adhering to the pole shoes 64 and 65 upon deenergization of the coils 18. To this end the antifreeze buttons are constructed from a material which is nonmagnetic and which does not tend to adhere to each other should a lm of oil accidentally become deposited on the armature. It has been found that the most suitable material from which to construct the antifreeze buttons 60, 61, 62 and 63 is tungsten, `since this material not only has the properties outlined above but is also able to withstand a large amount of use without being worn away. Since selector magnet armatures must be able -to withstand literally billions of operations during their life time it is important that the antifreeze buttons employed thereon be very resistive to wear. The antifreeze buttons may be attached to the armature and to the pole shoes by any suitable method, such as brazing.

Upon energization of the coils 18 the armature 45 will move toward lthe pole faces 64 and 65 due tothe generated magnetomotive force since the armature 45 is constructed from a magnetic material. In moving toward the pole faces 64 and 65 the armature will, of course, pass from its retracted position which is .shown in FIG. 1 through an intermediate position such as that shown in FIG. 2 to its fully attracted position which is shown in FIG. 3. During the initial part of this movement the armature will rock around the pivot edge 66 of the hinge blocks 30 and 31 and will continue to rock about this edge until antifreeze button 61 comes into contact with antifreeze button 63. At this point, which is shown in FIG. 2, the armature will begin to rock about the antifreeze button 61 and will become disassociated from the pivot edge 66. The armature will continue to rock about antifreeze button 61 until antifreeze button 60 comes in contact with antifreeze button 62, at which time the movement of the armature toward the pole faces will be completed and the armature will be in the position shown in FIG. 3.

At the -time the armature ceases to pivot about the pivot edge 66 of the hinge blocks 30 and 31 and starts to pivot about the antifreeze button 61 the force of the retracting spring 52 on the armature will be greatly increased. This is because the lever arm through which the retracting spring 52 operates on -the armature 45 during its ini-tial portion of its movement is relatively small, ie., the distance between the pivot edge 66 and the point of attachment of the retracting spring 52 to the projecting arm 67 of the armature 45, whereas when the armature is pivoting about the antifreeze button 61 the lever arm through which the retracting spring 52 operates on the Y armature 45 is relatively long, i.e., the distance between the point of attachment of the spring 52 to arm 67 and the center of the antifreeze button 61. As may be seen in the drawings the lever arm through which the spring 52 operates on the armature 45 during the latter portion of this movement is approximately six times longer than the lever arm through which the spring operates on the armature during the initial portion of its movement. This causes the leverage exerted by the spring 52 on the armature 45 to be approximately six times greater and thereby causes the armature to be subjected to a very high retracting force at the time when it is in its fully attracted position (FIG. 3). This phenomenon, in conjunction with the properties of the antifreeze buttons 60, 61, 62, and 63, overcomes the tendency of the armature to adhere to the pole shoes 25 and 26 and thereby causes the armature to quickly and posi-tively move away from the pole shoes when the coils 18 are deenergized. This in turn causes the armature of the present invention to quickly and positively return to position to respond to incoming message bearing electrical signals and thus reduces the possibility that the armature will not faithfully follow the signals.

The exible connecting member 40, which serves to attach the armature 45 to the hinge blocks 30 and 31 in the manner pointed out hereinbefore, is constructed from a very thin sheet of metal and serves to prevent the armature 45 from moving in the horizontal plane while allowing the armature to rock upward during its travel toward the pole faces. Thus, as the armature moves from the position shown in FIG. l to the position shown in FIG. 3, the flexible connecting member 40 is deformed into a curved conguration and is positively moved away from the pivot edge 66. As the .armature rocks about the pivot edge 66 during the initial portion of its movement toward the pole shoes the flexible connecting member 40 allows the armature to remain in contact with the pivot edge; however, when the armature rocks about the lantifreeze button 61 during the latter portion of its movement toward the pole shoes the flexible connecting member 4t) allows the armature to move away from the pivot edge 66 and thus increases the lever arm through which the retracting spring 52 operates on the armature 45. This feature of the invention permits the retracting force applied to the armature 45 during the initial portion of its movement toward the pole shoes to be relatively small when compared with the retracting force which is applied to the armature when it approaches its fully attracted position. This is very effective since the air gap between the armature and the pole shoe is fairly large when the armature is in .its retracted position and thus the magnetomotive force on the armature due to the presence of the llux eld through the core 17, the pole shoes 25 and 26 and armature is relatively weak. However, when the armature has moved to the partially attracted position shown in FIG. 2, the force imposed on the armature by the flux eld is greatly increased since the air gap between the pole shoe and the armature has been greatly decreased. Therefore, it is permissible at this point to sharply increase the retracting force on the armature since such an increase in force will not appreciably retard the armature in its movement toward the pole shoes and since, as has been pointed out hereinbefore, a very high retracting force is necessary when the armature is in its fully attracted position so that any tendency of the armature to adhere to the pole shoe may be overcome.

Although only one embodiment of the invention is shown in the drawings and described in the foregoing specification, it will be understood that invention is not limited to the specific embodiment described, but is capable of modification and rearrangement and substitution of parts and elements without departing from the spirit of the invention.

What is claimed is:

1. An electromagnet assembly comprising:

a frame;

-a core mounted on the frame and having pole faces;

means for generating a flux field through the core;

an armature for actuation toward the pole faces by the generated flux field;

a flexible member fixed to the frame and to the armature to form a hinge connection between them.;

urging means attached to the armature at a point intermediate the point of attachment of the armature to the flexible member and the point of attachment of the flexible member to the frame for urging the free end of the armature away from the pole faces;

means positioned intermediate the point of attachment of the urging means to the armature and the point of attachment of the flexible member to the armature for pivoting the armature during the first part of its movement toward the pole faces; and

means positioned on the armature at a point intermediate its free end and its point of attachment to the fiexible member for pivoting the armature during the second part of its movement toward the pole faces and for increasing the effective forces of the urging means in urging the free end of the armature away from the pole faces.

2. An electromagnet assembly comprising:

a frame;

a core mounted on the frame;

at least one coil surrounding the core for generating a flux field through the core;

an armature for actuation by the flux field;

a flexible member fixed to the frame and to the ar-mature to form a connection between them;

a spring attached to the armature at a point intermediate the point of attachment of the larmature to the flexible member and the point of attachment of the flexible member to the frame for urging the free end of the armature away from the core;

a pivot edge on the frame to form a first pivot for the armature upon attraction of the .armature toward the core by the fiux field, and

an abutment positioned on the armaature at a pomt intermediate its free end and its point of attachment to the fiexible member to provide a second pivot about which the armature rocks to increase the effective force of the spring in opposing the flux field upon further attraction of the armature toward the core.

3. In a magnet assemblage having a core, and armature and an energizing winding for generating an electromagnetic field to attract the armature to the core,

a frame for supporting said core, winding and armature meansfor hingedly attaching one end of said armature to said frame;

an arm on said one end of the armature extending 4away from the core;

means attached to said arm and the frame for biasing the other end of said armature away from said core;

a pivot edge formed on said frame intermediate the core and the point of attachment of the biasing means to said arm about which said armature pivots during the initial and terminal portions respectively of its movement toward and away from the core; and

a pivot projection on the armature more remote from the biasing means than the pivot edge for engaging the core to provide a second pivot for the armature in the intermediate portion of its travel toward and away from the core thereby to increase the biasing effect of the biasing means when the armature is closest to the core.

4. In a magnet structure,

a core providing at least two pole faces for the magnet;

at least one coil for generating a magnetic field in the core;

an armature for movement toward the pole faces by the magnetic field;

a spring attached to one end of the armature for continuously urging the armature away from the pole faces and effective to move the armature away from the pole faces when the magnetic field is broken down;

a first pivot about which the armature rocks during a first portion of its movement toward the pole faces, said pivot being positioned between the point of attachment of the spring to the armature and the core; and

a second pivot about which the armature rocks during the remainder of its movement toward the pole faces, said second pivot being located on the armature and between the first pivot and the free en-d of the armature and being effective to disengage the armature from the first pivot thereby to increase the effect of the spring on the armature.

5. In a selector magnet for a printing telegraph receiver having a U-shaped core, two coils carried by the legs of said core and energizable to generate a fiux field through the core and an armature which moves toward the core when the flux field is generated and which moves away from the core when the fiux field is broken down, an armature support and biasing assembly comprising:

a spring for biasing the armature away from the core,

said spring being attached to one end of the armature;

a flexible member for supporting the armature during its movement toward and away from the core, said flexible member being .attached to the armature at a point intermediate the core and the point of attachment of the spring to the armature;

a member having an edge forming a first pivot for the armature during the initial and terminal portions of its movement toward and away from the core, said edge being located between the point of' attachment of the spring to the armature and the point of attachment of the armature to the fiexible member; and

a projection on the armature located at a point intermediate its free end and the first pivot and forming a second pivot for the armature during the intermediate portion of its travel toward and away from the core, said projection disengaging the armature from the first pivot and increasing the biasing effect of the spring on the armature.

6. Xselector magnet for a printing telegraph receiver comprising:

a frame;

.a core attached to the frame, said core having two pole faces;

means for generating a flux field through the core;

an armature for movement toward the pole faces by said field and for movement away from the pole faces when said field is broken down;

a fiexible connecting member for attaching the armature to the frame, said flexible connecting member having one of its ends attached to the frame and extending beyond an edge of the frame and having the other of its ends attached to the armature;

.a spring for continuously urging the armature away from the pole faces and effective to move the armature away from the pole faces when the fiux field is broken down, said spring being attached to the armature at a point intermediate the point of attachment of the flexible member to the frame and the point of .attachment of the flexible member to the armature;

said edge of the frame forming a pivot for the armature during the initial portion of its movement toward the pole faces;

a non-magnetic Wear-resistant insert in each pole face;

a pair of non-magnetic, wear-resistant armature inserts positioned to `come in contact with the pole face inserts when the armature moves toward the pole faces, `one of said armature inserts and its-corresponding pole face insert serving as a pivot for the armature during the latter portion of its movement toward the pole faces land also serving to disengage the armature from said edge and thereby to increase signicantly the urging effect of the springv on the armature.

AReferences Cited by the Examiner UNITED STATES PATENTS Baynard 178-100 Schmidt 317-165 2/ 1944 Lloyd.

References Cited by the Applicant UNITED STATES PATENTS Berdon. Putt. Erickson. Buchet a1. Ogle. Orsatti et al. Deer et al. 

1. AN ELECTROMAGNET ASSEMBLY COMPRISING: A FRAME; A CORE MOUNTED ON THE FRAME AND HAVING POLE FACES; MEANS FOR GENERATING A FLUX FIELD THROUGH THE CORE; AN ARMATURE FOR ACTUATION TOWARD THE POLE FACES BY THE GENERATED FLUX FIELD; A FLEXIBLE MEMBER FIXED TO THE FRAME AND TO THE ARMATURE TO FORM A HINGE CONNECTION BETWEEN THEM; URGING MEANS ATTACHED TO THE ARMATURE AT A POINT INTERMEDIATE THE POINT OF ATTACHMENT OF THE ARMATURE TO THE FLEXIBLE MEMBER AND THE POINT OF ATTACHMENT OF THE FLEXIBLE MEMBER OT THE FRAME FOR URGING THE FREE END OF THE ARMATURE AWAY FROM THE POLE FACES; MEANS POSITIONED INTERMEDIATE THE POINT OF ATTACHMENT OF THE URGING MEANS TO THE ARMATURE AND THE POINT OF ATTACHMENT OF THE FLEXIBLE MEMBER TO THE ARMATURE FOR PIVOTING THE ARMATURE DURING THE FIRST PART OF ITS MOVEMENT TOWARD THE POLE FACES; AND MEANS POSITIONED ON THE ARMATURE AT A POINT INTERMEDIATE ITS FREE END AND ITS POINT OF ATTACHMENT TO THE FLEXIBLE MEMBER FOR PIVOTING THE ARMATURE DURING THE SECOND PART OF ITS MOVEMENT TOWARD THE POLE FACES AND FOR INCREASING THE EFFECTIVE FORCES OF THE URGING MEANS IN URGING THE FREE END OF THE ARMATURE AWAY FROM THE POLE FACES. 